Won-Gyu Lim

Multiple band-notched planar monopole antenna for multiband wireless systems

A multiple band-notched planar monopole antenna for multiband wireless systems is presented. The proposed antenna consists of a wideband planar monopole antenna and the multiple U-shape slots, producing band-notched characteristics. In order to generate two band-notched characteristics, we propose that three U-shape slots are required. This technique is suitable for creating ultra-wideband (UWB) antenna with narrow frequency notches or for creating multiband antennas.

Design of Low-Cost Chipless System Using Printable Chipless Tag With Electromagnetic Code

In this letter, a printable chipless tag with electromagnetic code using split ring resonators is proposed. A 4 b chipless tag that can be applied to paper/plastic-based items such as ID cards, tickets, banknotes and security documents is designed. The chipless tag generates distinct electromagnetic characteristics by various combinations of a split ring resonator. Furthermore, a reader system is proposed to digitize electromagnetic characteristics and convert chipless tag to electromagnetic code.

High Isolation Internal Dual-Band Planar Inverted-F Antenna Diversity System with Band-Notched Slots for MIMO Terminals

Internal dual-band planar inverted-F antenna (PIFA) diversity system for portable devices, operating in the 2.4-GHz band (2400-2484MHz) and 5.2-GHz band (5150-5350MHz), is presented. To reduce the mutual coupling and get the high isolation between the two internal dual-band antennas, we proposed the band-notched lambda/4 slots on the ground plane. The optimized band-notched slots for high isolation, high radiation efficiency and high effective diversity gain are analyzed. The band-notched slots can be used to the small MIMO terminals which require high isolation between antennas

RFID Reader Front-End Having Robust Tx Leakage Canceller for Load Variation

A novel front-end structure for ultra-high-frequency RF identification reader is proposed. The proposed front-end consists of a balanced coupler and four-port feed antenna system. The proposed balanced coupler structure has high transmit/receiver isolation feature and good insensitivity to load variations. The proposed four-port feed antenna system is applied for removing the coupling among antennas, which deteriorates the isolation. The proposed system is numerically analyzed and verified experimentally as well.

Design of Compact Quadruple Inverted-F Antenna With Circular Polarization for GPS Receiver

A compact quadruple inverted-F antenna (QIFA) with right-hand circular polarization for global positioning system (GPS) receiver is presented. The proposed QIFA consists of four spiral-shaped inverted-F antennas fed by a compact multilayered feed network. In order to improve the radiation efficiency of four-port feed antenna like QIFA, we analyze an optimum matching method considering both reflection coefficient at each port and the mutual coupling between ports simultaneously. Experimental results show that QIFA of size 10 x 10 x 12 mm3 has a 3-dB beamwidth of more than 130°, the peak gain of -1 dBic and the axial ratio under 2 dB.

Integrated Planar Monopole Antenna With Microstrip Resonators Having Band-Notched Characteristics

Novel integrated planar monopole antennas with various microstrip resonators are presented. The proposed integrated antennas consist of wideband planar monopole antennas and electromagnetically coupled microstrip resonators producing band-notched characteristics. Various types of microstrip resonators such as open-circuited line resonator, short-circuited line resonator, closed-loop resonator and open-loop resonator are described. The proposed designs are suitable for wideband antennas with narrowband interferer rejection characteristic or multi-band antennas.

Tunable Band-notched Ultra Wideband (UWB) Planar Monopole Antennas Using Varactor

A new tunable band-notched ultra wideband (UWB) planar monopole antenna is presented. The proposed antenna consists of a wideband planar monopole antenna, resonating stubs and varactor diodes. In order to generate tunable band-notched characteristic, we applied quarter-wavelength stubs with varactor diode to the wideband planar monopole antenna. We interpret the mechanism for notch characteristics using surface current distributions. This new approach is suitable for designing wideband antenna with narrow band interferer rejection characteristics.

Compact Integrated Antenna With Circulator for UHF RFID System

A passive UHF radio frequency identification (RFID) reader antenna with high transmit/receive isolation, which consists of two quadrifilar spiral antennas (QSAs) and the feeding networks, is proposed. The high isolation can be achieved by two concentric, circularly polarized antennas and 4-point feed circuits, which make the same circular polarization. The simulated and experimental results show that the transmit/receive isolation is more than 40 dB and the gains of two QSAs are 1.0 dBi for the inner QSA and 0.7 dBi for the outer QSA at the 910 MHz, respectively.

24 GHz Balanced Doppler Radar Front-End With Tx Leakage Canceller for Antenna Impedance Variation and Mutual Coupling

A new balanced Doppler radar front-end architecture with Tx leakage canceller for antenna impedance variation and antenna mutual coupling is proposed. Consisting of two quadrature hybrids, two ring hybrids and 4-port feed antenna system, the proposed balanced structure achieves high transmit/receive (Tx/Rx) isolation stable to antenna impedance variation and antenna mutual coupling. The proposed 4-port feed antenna is configured by dual fed 2 × 1 patch array having 6.97 dBi and 5.65 dBi of measured Tx and Rx peak gain, respectively. In addition, the proposed architecture undergoes no power loss in both transmit and receive paths, and obtains the measured Tx/Rx isolation of more than 45 dB stable at 24 GHz regardless of the load variation. The proposed architecture that can determine the speed as low as 0.5 mm/s (0.078 Hz Doppler shift) is theoretically and experimentally analyzed for high isolation despite of antenna mismatch.

Printed square quadrifilar spiral antenna for UHF RFID reader

This paper proposes the printed square quadrifilar spiral antenna (QSA) for mobile RFID reader. A folded inverted-F antenna structure is used as a spiral to increase the impedance of QSA. Results show that the array antenna has obtained a sharp 3 dB beamwidth, high gain and good axial ratio.